The present invention is generally directed to apparatus and methods to aid in the generation of chemical libraries of known compositions and, more particularly, to automated fluid dispensing and distniution assemblies, including wash stations, used during generation of chemical libraries.
The relationship between structure and function of molecules is a fundamental issue in the study of biological and other chemistry-based systems. Structure-function relationships are important in understanding, for example, the function of enzymes, cellular communication, and cellular control and feedback mechanisms. Certain macromolecules are known to interact and bind to other molecules having a specific three-dimensional spatial and electronic distribution. Any macromolecule having such specificity can be considered a receptor, whether the macromolecule is an enzyme, a protein, a glycoprotein, an antibody, or an oligonucleotide sequence of DNA, RNA or the like. The various molecules which bind to receptors are known as ligands.
A common way to generate such ligands is to synthesize molecules in a stepwise fashion on solid phase resins. Since the introduction of solid phase synthesis methods for peptides, oligonucleotides and small organic molecules, new methods employing solid phase strategies have been developed that are capable of generating thousands, and in some cases even millions, of individual molecules using automated or manual techniques. These synthesis strategies, which generate families or libraries of molecules, are generally referred to as xe2x80x9ccombinatorial chemistryxe2x80x9d or xe2x80x9ccombinatorial synthesisxe2x80x9d strategies. In the pharmaceutical industry these families or libraries of molecules are often formatted into 96 well plates. This formatting provides a convenient method to screen these molecules to identify novel ligands for biological receptors.
To aid in the generation of combinatorial chemical libraries, scientific instruments have been produced which automatically perform many or all of the chemical steps required to generate such libraries. An example of an automated combinatorial chemical library synthesizer is described in PCT Patent Application No. WO 97/14041, published Apr. 17, 1997, assigned to the assignee of the present invention, and incorporated herein in its entirety by reference. Another example of an automated combinatorial chemical library synthesizer is the Model 396 MPS fully automated multiple peptide synthesizer, manufactured by Advanced ChemTech, Inc. (xe2x80x9cACTxe2x80x9d) of Louisville, Ky. A further example of an automated combinatorial chemical library synthesizer is described in U.S. Pat. No. 5,609,826, entitled xe2x80x9cMETHODS AND APPARATUS FOR THE GENERATION OF CHEMICAL LIBRARIES,xe2x80x9d issued Mar. 11, 1997, assigned to the assignee of the present invention, and incorporated herein in its entirety by reference.
In such automated chemical library synthesizers, many different molecules are synthesized simultaneously on solid supports, with a different molecule or set of molecules being synthesized in each reaction chamber. One set of reagents is added to the solid support before the addition of the next successive set of reagents is added. Thus, each growing molecule or set of molecules is the sized in a stepwise fashion via the addition of sets of input reagents into each reaction chamber.
As is known to those skilled in the art, the process of combinatorial synthesis not only requires the introduction of a series of reagents, but also requires washing, deblocking, capping, and other reaction steps as well. These steps must be performed regardless of the sequence in which the various reagent sets are introduced into the reaction chambers.
In some automated combinatorial chemical library synthesizers, which incorporate pipetting workstations such as the TECAN 5032 (manufactured by TECAN AG, Feldbachstrasse 80, CH-8634 Hombrechtiken, Switzerland), only one or two pipetting needles can be used to introduce the reagents or solvents used in the washing, deblocking, capping, or other commonly performed steps. Since these steps can be performed simultaneously in all of the reaction chambers, the use of only one or two pipetting needles to introduce the appropriate reagents or solvents creates a significant increase in the length of time needed to synthesize a combinatorial chemical library.
Another limiting factor in the time to produce a combinatorial chemical library is the use of an immovable reaction block installed on the operating deck of a pipetting work station. If all the procedural steps for synthesizing a chemical library must take place while the reaction block is located on the operating deck of a pipetting work station, the work station is filly occupied for the duration of the chemical synthesis. This duration may encompass hours or even days for a reaction sequence to be completed. On the other hand, the use of a movable reaction block (such as employed by Cargill and Maiefski in U.S. Pat. No. 5,609,826) allows one to employ a variety of pipetting work stations.
Yet another limiting factor in the time to produce a combinatorial chemical library is the use of a non-standard format reaction block. The use of a reaction block with 96 chambers, which allows one to synthesize combinatorial chemical libraries on 96-well microtiter plate format (with the wells on 9 mm centers), reduces the time involved in pipetting libraries into a standard 96-well format after synthesis. Thus, these libraries can be screened directly against a variety of receptors, without reformatting. For an example of such a reaction block see Cargill and Maiefski in U.S. Pat. No. 5,609,826.
Each pipetting work station may be uniquely tailored to a specific task required in the chemical synthesis (see Cargill and Maiefski in U.S. Pat. No. 5,609,826). The function of each pipetting work station may be to deliver individual reagents or sets of reagents to specific locations in a reaction block. Alternatively, the finction of a pipetting work station may be to deliver an individual reagent or set of reagents to all locations of the reaction block. The function of such work stations may be best tailored to a specific set of pipetting tasks. As is known to those skilled in the art, many chemical steps that require washing, deblocking, capping, etc. are best performed simultaneously, or in other words, in parallel, in a reaction block. Thus the pipetting or delivery of washing solvents, deblocking and capping reagents, or other reagents common to all locations in the reaction block is also best performed in parallel.
The wash station described in WO 97/14041 provides a significantly improved automated wash station that has an array of 96 pipetting needles that simultaneously introduce reagents or solvents into the 96 reaction chambers in the reaction blocks. Accordingly, a synthesizing step of washing, deblocking, capping, or the like of multiple samples is done in parallel, thereby reducing the time and cost of generating a combinatorial chemical library. The synthesizing process, however, still includes time-consuming steps. For example, different reaction blocks having different samples therein often require the use of different solvents during a washing step. Furthermore, changing between solvents for washing, or changing between reagents for deblocking, for example, also includes time-consuming steps. Changing between solvents and recalibrating the wash station to provide the appropriate amount of a selected solvent for each sample can be a difficult and time-consuming process;
Other difficulties experienced by the conventional wash stations include accurately distributing a selected amount of solvent or reagent to all of the needles for simultaneous distribution into the reaction chambers. Failure to use accurate amounts of the solvent or reagent can provide inaccurate results, compromise the synthesizing process, and jeopardize the reliability of the chemical library. Such difficulties are magnified when trying to distribute the selected solvent or reagent to a large number of pipetting needles, such as an array of ninety-six needles.
A further difficulty experienced in synthesizing processes is that the same wash station typically uses a variety of halogenated and non-halogenated solvents. Disposal of the halogenated solvent can be a laborious and costly process, because disposal of the halogenated solvents must be carefully controlled for legal and environmental reasons. Disposal of the non-halogenated solvents, on the other hand, is less rigorous. Accordingly, the waste solvents are separated between halogenated and non-halogenated solvents. The separation process, however, has been a difficult process to effectively perform efficiently and inexpensively. Therefore, there remains a need in the art for an apparatus and method for quickly and efficiently performing certain reaction steps (such as washing, deblocking, capping, etc.) simultaneously and for managing the waste products (such as halogenated and non-halogenated solvents) resulting from the reaction steps.
The present invention provides a fluid dispensing assembly for dispensing a selected fluid into multiple vessels and methods of dispensing selected fluids or samples that overcome the drawbacks experienced by the prior art and provides further related advantages. In one embodiment of the invention, the fluid dispensing system includes a distribution manifold with a manifold inlet positioned to receive fluid from the fluid source. The distribution manifold has a plurality of distribution channels that are all coupled to the manifold inlet. The distribution channels each have a separate channel outlet through which the fluid can flow. Each distribution channel also has a valve therein to allow the fluid to flow in one direction in the respective distribution channel. An array of fluid dispensers is connected to the distribution manifold. Each fluid dispenser is connected to the channel outlet of a respective distribution channel to receive the fluid passing through the channel outlet. Each fluid dispenser has a valve therein to allow the fluid to flow in one direction out of the respective fluid dispenser.
In another embodiment of the invention the fluid dispensing system is a wash station assembly connectable to a plurality of solvent sources by separate solvent lines. The wash station includes a solvent dispensing assembly connected to a frame, and the solvent dispensing assembly has a selector valve that is connectable to the solvent lines. The selector valve is adjustable between a plurality of positions, and each position allows only one of the solvents to pass through the selector valve at a time.
The selector valve is connected by a distribution manifold to an array of solvent-retaining members, such as syringes or the like, so the solvent passing through the selector valve is distributed to the syringes via the distribution manifold The distribution manifold has a manifold inlet connected to the selector valve and positioned to receive the solvent from the selector valve. The distribution manifold has a plurality of distribution channels that communicate with the manifold inlet, and each distribution channel is connected to a respective one of the syringes. The distribution channels each have an outlet that directs the solvent into the respective syringe. The syringes are connected to an array of distributor members, such as pipetting needles or the like, that receive the solvent dispensed from the syringes. Pipetting needles and syringes are positionable relative to a sample containing assembly, such as a reaction block or the like, to dispense the solvent into samples within the sample containing assembly.
In one embodiment of the invention, the wash station assembly includes a programmable controller that is operatively connected to the selector valve to control the position of the selector valve, and thus control the solvent passing therethrough to the distribution manifold. The selector value also includes a position sensor coupled to the controller so the controller can monitor and identify the selector valve""s position, thereby monitoring which solvent is passing through the selector valve.
In one embodiment, the solvent dispensing assembly is movably connected to a distributor support, and the distributor support is movably connected to the frame, so the solvent distributing assembly is movable as a unit laterally and vertically relative to the frame. The solvent dispensing assembly has the array of syringes extending between the distribution manifold and an upper support plate. The upper support plate is movable relative to the distribution manifold between upper and lower positions. The syringes are extended and moved along an aspirating stroke to fill each syringe with a selected amount of the solvent when the upper support plate is moved from the lower position to the upper position. The syringes are compressed and movable through a discharge stroke to discharge the solvent through the respective pipetting needles when the upper support plate is moved from the upper position to the lower position. A check valve is positioned in each distributor channel in the distribution manifold to prevent backflow of the solvent out of the syringe during the syringe""s dispensing stroke.
Each syringe receives the solvent from the distribution manifold during the aspirating stroke through an inlet port formed in a syringe connector, which is removably connected to the distribution manifold. The connector also includes an outlet port that directs the solvent out of the syringe into the pipetting needle during the dispensing stroke. A valve, such as a check valve, is positioned in the outlet port to allow the solvent to flow out of the syringe while preventing the solvent or air from entering the syringe through the outlet port during the aspirating stroke. The check valve also prevents solvent from flowing into the distribution manifold from the syringe during the discharge stroke. Accordingly, the solvent has a one-way path into the syringe from the distribution manifold and a one-way path out of the syringe through outlet port and the pipetting needle.
In another embodiment of the invention, the wash station assembly includes a waste management system connected to the wash station to receive waste solvent from the wash station. The waste management system includes a flow control valve that selectively directs the waste solvent to a first or second waste solvent receptacle, depending upon the type of solvent discharged from the wash station. The flow control valve is coupled to the controller, which is connected to the selector valve, and the controller automatically adjusts the flow control valve""s position based upon the type of solvent (e.g. a halogenated or non-halogenated solvent) that is passed through the selector valve. Accordingly, the waste management system provides for automated separation of solvents used by the wash station.
The present invention also provides a method for washing a selected sample in a wash station assembly. In one embodiment of the invention, the method includes the steps of passing a plurality of solvents through separate solvent lines to an adjustable selector valve of a wash station assembly, adjusting the selector valve to allow one of the solvents to flow through the selector valve to a distributor manifold, and substantially simultaneously distributing with the distributor manifold a selected amount of the solvent into a plurality of solvent distributing assemblies. The method further includes substantially simultaneously dispensing the solvent from the solvent distributing assemblies into a plurality of sample containers, and washing the samples in the sample containers.
In another embodiment of the invention, the method includes the steps of determining if the solvent is a halogenated or a non-halogenated solvent, removing the solvent from the sample containers, and directing the solvent into a waste line that is connected to a first waste receptacle for halogenated solvents and a second waste receptacle for non-halogenated solvents. The method further includes positioning a flow control valve, which is connected to the waste line, in a first position when the solvent is a halogenated solvent to direct the halogenated solvent to the first receptacle. The method further includes positioning the flow control valve in a second position when the solvent is a non-halogenated solvent to direct the solvent to the second waste receptacle.
A further embodiment of the method includes the steps of adjusting the selector valve from a first position to a second position to allow only a second one of the solvents to pass through the selector valve, with the other solvents being blocked from passing through the selector valve. The method further includes distributing the second solvent into the solvent distributing assemblies, dispensing the second solvent into sample containers, and washing samples in the sample containers.